linux-kernel - Re: [PATCH v2 00/15] Introduce threaded trace streaming for basic perf record operation

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Date:   Tue, 27 Oct 2020 13:10:13 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 00/15] Introduce threaded trace streaming for basic
 perf record operation

On Mon, Oct 26, 2020 at 08:59:01PM +0300, Alexey Budankov wrote:
> 
> On 24.10.2020 18:43, Jiri Olsa wrote:
> > On Wed, Oct 21, 2020 at 06:52:43PM +0300, Alexey Budankov wrote:
> >>
> >> Changes in v2:
> >> - explicitly added credit tags to patches 6/15 and 15/15,
> >>   additionally to cites [1], [2]
> >> - updated description of 3/15 to explicitly mention the reason
> >>   to open data directories in read access mode (e.g. for perf report)
> >> - implemented fix for compilation error of 2/15
> >> - explicitly elaborated on found issues to be resolved for
> >>   threaded AUX trace capture
> >>
> >> v1: https://lore.kernel.org/lkml/810f3a69-0004-9dff-a911-b7ff97220ae0@linux.intel.com/
> >>
> >> Patch set provides threaded trace streaming for base perf record
> >> operation. Provided streaming mode (--threads) mitigates profiling
> >> data losses and resolves scalability issues of serial and asynchronous
> >> (--aio) trace streaming modes on multicore server systems. The patch
> >> set is based on the prototype [1], [2] and the most closely relates
> >> to mode 3) "mode that creates thread for every monitored memory map".
> > 
> > so what I liked about the previous code was that you could
> > configure how the threads would be created
> > 
> > default --threads options created thread for each cpu like
> > in your change:
> > 
> >   $ perf record -v --threads ...
> >   ...
> >   thread 0 monitor: 0 allowed: 0
> >   thread 1 monitor: 1 allowed: 1
> >   thread 2 monitor: 2 allowed: 2
> >   thread 3 monitor: 3 allowed: 3
> >   thread 4 monitor: 4 allowed: 4
> >   thread 5 monitor: 5 allowed: 5
> >   thread 6 monitor: 6 allowed: 6
> >   thread 7 monitor: 7 allowed: 7
> 
> Yes, it is configurable in the prototype. Even though this patch set
> doesn't implement that parameters for --thread option, just because
> VTune doesn't have use cases for that yet, it has still been designed
> and implemented with that possible extension in mind so it could then
> be easily added on top of it.

I'm not sure about vtune extensions, but if we are going to
have --threads option I believe we should make it configurable
at least to the extend descibed below

jirka

> 
> > 
> > 
> > then numa based:
> > 
> >   $ perf record -v --threads=numa ...
> >   ...
> >   thread 0 monitor: 0-5,12-17 allowed: 0-5,12-17
> >   thread 1 monitor: 6-11,18-23 allowed: 6-11,18-23
> > 
> > 
> > socket based:
> > 
> >   $ perf record -v --threads=socket ...
> >   ...
> >   thread 0 monitor: 0-7 allowed: 0-7
> > 
> > 
> > core based:
> > 
> >   $ perf record -v --threads=core ...
> >   ...
> >   thread 0 monitor: 0,4 allowed: 0,4
> >   thread 1 monitor: 1,5 allowed: 1,5
> >   thread 2 monitor: 2,6 allowed: 2,6
> >   thread 3 monitor: 3,7 allowed: 3,7
> > 
> > 
> > and user configurable:
> > 
> >   $ perf record -v  --threads=0-3/0:4-7/4 ...
> >   ...
> >   threads: 0. monitor 0-3, allowed 0
> >   threads: 1. monitor 4-7, allowed 4
> > 
> > 
> > so this way you could easily pin threads to cpu/core/socket/numa,
> > or to some other cpu of your choice, because this will be always
> > game of try and check where I'm not getting LOST events and not
> > creating 1000 threads
> > 
> >  perf record: Add support for threads numa option value
> >  perf record: Add support for threads socket option value
> >  perf record: Add support for threads core option value
> >  perf record: Add support for threads user option value
> 
> Makes sense.
> 
> Alexei
>